Multi-antenna signal receiving device processing multi-path interference

ABSTRACT

Described herein is a multi-antenna signal receiving device that includes a plurality of reception antennas that is capable of maximizing a diversity gain while eliminating a multi-path interference (MPI). The device receives a first received signal of a first antenna that includes components corresponding to a plurality of first paths and the device receives a second received signal of a second antenna that includes components corresponding to a plurality of second paths. The multi-antenna signal receiving device detects a component corresponding to a first path among the plurality of first paths, and a component corresponding to a second path among the plurality of second paths.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(a) of aJapanese Patent Application No. 2008-290792 filed on Nov. 13, 2008 inthe Japanese Patent Office and a Korean Patent Application No.10-2009-0038886 filed on May 4, 2009 in the Korean Intellectual PropertyOffice, the entire disclosures of which are incorporated herein byreference for all purposes.

BACKGROUND

1. Field

The following description relates to a receiving device including aplurality of reception antennas, and more particularly, to a technologythat may maximize a diversity gain, while reducing or eliminating amulti-path interference (MPI).

2. Description of Related Art

Researches have been conducted to provide various multimedia servicesthat support a high quality and a high data transmission rate, in awireless communication environment. As part of the research, atechnology related to a multi-input multi-out (MIMO) system that uses aplurality of channels in a spatial area has been developed.

The MIMO technology uses multiple antennas to increase a number ofchannel bits in a limited frequency resource, and provides a high datatransmission rate. The MIMO technology uses multipletransmission/reception antennas in an environment where one or morescatterers exist, to provide a channel capacity proportional to asmaller number of antennas, between the transmission antennas and thereception antennas.

In the MIMO communication system, a plurality of channels exist betweena transmitting device and a receiving device. As an example, when anumber of antennas of the transmitting device and a number of antennasof the receiving device are four, a received signal Y may be expressedas given in the exemplary Equation 1 below.

$\begin{matrix}\begin{matrix}{Y = \begin{bmatrix}y_{1} \\y_{2} \\y_{3} \\y_{4}\end{bmatrix}} \\{= {{\begin{bmatrix}h_{11} & h_{12} & h_{13} & h_{14} \\h_{21} & h_{22} & h_{23} & h_{24} \\h_{31} & h_{32} & h_{33} & h_{34} \\h_{41} & h_{42} & h_{43} & h_{44}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\x_{3} \\x_{4}\end{bmatrix}} + \begin{bmatrix}n_{1} \\n_{2} \\n_{3} \\n_{4}\end{bmatrix}}} \\{= {{HX} + N}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In this example, the symbols x₁, x₂, x₃, and x₄ are transmissionsymbols, h_(ab) is a channel coefficient corresponding to a path until ab^(th) transmission symbol reaches an a^(th) receiving antenna, and n₁,n₂, n₃, and n₄ are noise.

The receiving device separates a received signal into a plurality ofstreams and performs detection. The streams, for example, thetransmission symbols, transmitted from the transmitting device aredifficult to accurately detect when multi-path interference (MPI)exists.

SUMMARY

In one general aspect, provided is a multi-antenna signal receivingdevice, comprising at least two antennas to receive at least one stream,a received signal of a first antenna including components correspondingto a plurality of first paths and a received signal of a second antennaincluding components corresponding to a plurality of second paths, afirst detector to detect a component corresponding to a first path ofthe plurality of first paths from among components included in thereceived signal of the first antenna, and to detect a componentcorresponding to a second path of the plurality of second paths fromamong components included in the received signal of the second antenna,a second detector to detect a component corresponding to the remainingfirst paths of the plurality of first paths from among the componentsincluded in the received signal of the first antenna, and to detect acomponent corresponding to the remaining second paths of the pluralityof second paths from among the components included in the receivedsignal of the second antenna, and a combining unit to combine thedetected component from the first detector and the detected componentfrom the second detector, to detect the at least one stream.

The device may further comprise a QR decomposition unit to perform QRdecomposition with respect to a channel matrix based on the received atleast one stream, to calculate a Q matrix and an R matrix.

The first detector may remove a multi-path interference existing in thereceived signal using at least one stream detected from a prioriteration, extract the component corresponding to the first path fromamong the components included in the received signal of the firstantenna, and detect the at least one stream using the Q matrix and the Rmatrix.

The first detector may comprise a first multi-path interferenceeliminating unit to remove a multi-path interference existing in thereceived signal of the first antenna using at least one stream detectedfrom a prior iteration, and to extract the component corresponding tothe first path from among the components included in the received signalof the first antenna.

The first path may have a higher gain than the remaining first paths ofthe plurality of first paths.

The first detector may further comprise a first Q matrix transformer totransform the component corresponding to the first path of the pluralityof first paths using the Q matrix.

The first detector may further comprise a plurality of first frequencydomain equalizers (FDEs) to perform equalization of an output of thefirst Q matrix transformer in a frequency domain prior to performingInverse Fourier Transform.

The first detector may further comprise a plurality of first InverseDiscrete Fourier Transformers (IDFTs) to perform Inverse DiscreteFourier Transform with respect to outputs of the plurality of the firstFDEs.

The first detector may further remove a multi-path interference existingin the received signal of the second antenna using at least one streamdetected from a prior iteration, extract the component corresponding tothe second path from among the components included in the receivedsignal of the second antenna, and detect the at least one stream usingthe Q matrix and the R matrix.

The first multi-path interference eliminating unit further removes amulti-path interference existing in the received signal of the secondantenna using at least one stream detected from a prior iteration, andextracts the component corresponding to the second path from among thecomponents included in the received signal of the second antenna.

The second detector may comprise a second multi-path interferenceeliminating unit to remove a multi-path interference existing in thereceived signal of the first antenna using at least one stream detectedfrom a prior iteration, and to extract the component corresponding tothe remaining first paths from among the components included in thereceived signal of the first antenna.

The second multi-path interference eliminating unit may further remove amulti-path interference existing in the received signal of the secondantenna using at least one stream detected from a prior iteration, andextract the component corresponding to the remaining second paths fromamong the components included in the received signal of the secondantenna.

The second detector may further comprise a second Q matrix transformerto transform the component corresponding to the remaining first pathsand the component corresponding to the remaining second paths using theQ matrix.

The second detector may further comprise a plurality of second FDEs toperform equalization of an output of the second Q matrix transformer ina frequency domain prior to performing Discrete Inverse FourierTransform.

The second detector may further comprise a plurality of second IDFTs toperform Inverse Discrete Fourier Transform with respect to outputs ofthe plurality of second FDEs.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a two dimensional minimum mean squareerror (MMSE) based multi-antenna signal receiving device.

FIG. 2 illustrates an example of a QR decomposition-maximum likelihooddirection (QRD-MLD) multi-antenna signal receiving device.

FIG. 3 illustrates an example of a QRD engine-MLD (QRDE-MLD)multi-antenna signal receiving device utilizing frequency domainequalization.

FIG. 4 illustrates an operation of exemplary subtraction/addition units,an exemplary addition unit, and exemplary frequency domain equalizersthat may be incorporated into the QRDE-MLD multi-antenna receivingdevice of FIG. 3.

FIG. 5 illustrates a second example of a QRDE-MLD multi-antenna signalreceiving device.

FIG. 6 illustrates an exemplary addition unit and an exemplary frequencydomain equalizer that may be incorporated into the QRDE-MLDmulti-antenna signal receiving device of FIG. 5.

FIG. 7 illustrates an exemplary subtraction/addition unit and anexemplary frequency domain equalizer that may be incorporated into theQRDE-MLD multi-antenna signal receiving device of FIG. 5.

FIG. 8 is a diagram illustrating a multi-path interference (MPI).

FIG. 9 is a diagram illustrating an example of a multi-path interferencecanceller (MPIC)-QRDE-MLD multi-antenna signal receiving device.

FIG. 10 is a diagram illustrating a received signal of four receptionantennas, when four transmission antennas and the four receptionantennas are provided.

FIG. 11 illustrates detectors and combining units of an MPIC-QRDE-MLDmulti-antenna signal receiving device for processing the received signalof each of the four reception antennas of FIG. 10.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. Accordingly, various changes,modifications, and equivalents of the systems, apparatuses, and/ormethods described herein will be suggested to those of ordinary skill inthe art. Also, descriptions of well-known functions and constructionsmay be omitted for increased clarity and conciseness.

FIG. 1 illustrates an example of a two dimensional (2D)-minimum meansquare error (MMSE) based multi-antenna signal receiving device.

Referring to FIG. 1, a multi-antenna signal receiving device 100 mayinclude four receiving antennas, four fast Fourier transforms (FFTs) 110corresponding to the receiving antennas, the MMSE spatial filter 120,four frequency domain equalizers (FDEs) 130, four inverse discreteFourier transforms (IDFTs) 140, a parallel-to-serial (P/S) converter150, a log-likelihood ratio (LLR) detector 160, and a forward errorcorrection (FEC) 170.

In this example, it is assumed that a transmitting end transmittedtransmission symbols x₁, x₂, x₃, and x₄ via a channel H, as illustratedin Equation 1. The four receiving antennas of the multiple antennareceiver 100 receive four received symbols y₁, y₂, y₃, and y₄ as alsoshown in Equation 1.

The FFTs 110 may transform the received symbols y₁, y₂, y₃, and y₄ fromtime domain signals to frequency domain signals. The MMSE spatial filter120 may filter the received symbols y₁, y₂, y₃, and y₄ based on acoefficient disclosed in the following Equation 2:

$\begin{matrix}\frac{H^{H}}{{H^{H}H} + \frac{N}{S}} & \left\lbrack {{Equation}\mspace{20mu} 2} \right\rbrack\end{matrix}$

where S is the power of transmission symbols, and X^(H) denotesHermitian Transpose of X.

If a noise term is ignored, the coefficient disclosed in Equation 2 maybe represented as,

H^(H)/(H^(H)H).  [Equation 3]

The MMSE spatial filter 120 may perform an inner product operation for avector consisting of the received symbols and the coefficient disclosedin Equation 3, as illustrated by,

$\begin{matrix}\begin{matrix}{{\frac{H^{H}}{H^{H}H}Y} = {{\frac{H^{H}}{H^{H}H}{HX}} + {\frac{H^{H}}{H^{H}H}N}}} \\{= {X + {\frac{H^{H}}{H^{H}H}N}}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

From Equation 4, it can be known that the received symbols are separatedfor each substream.

The FDEs 130 may perform frequency domain equalization for an output ofthe MMSE spatial filter 120. By performing the frequency domainequalization, it is possible to compensate for distortion created bymulti-path interference.

The IDFTs 140 may transform outputs of the FDEs 130 from frequencydomain signals back to time domain signals. An output of the IDFTs 140may be multiplexed via the P/S converter 150.

The LLR detector 160 may detect a log-likelihood ratio (LLR) of anoutput of the P/S converter 150. The FEC 170 may perform errorcorrection based on the detected LLR.

The multi-antenna signal receiving device 100 of FIG. 1 may use atwo-dimensional MMSE scheme that processes a received signal based on anMMSE criterion, with respect to a frequency and a space, and maystruggle to obtain a diversity gain corresponding to a number of thereception antennas. For example, the multi-antenna signal receivingdevice 100 of FIG. 1 may compensate for the distortion when themulti-path interference is low. However, when the amount of multi-pathinterference is high, the multi-antenna signal receiving device 100 ofFIG. 1 may struggle to compensate for the distortion created by themulti-path interference.

FIG. 2 illustrates an example of a QR decomposition-maximum likelihooddirection (QRD-MLD) multi-antenna signal receiving device.

Referring to FIG. 2, the QR decomposition-based QRD-MLD multi-antennasignal receiving device 200 may include four reception antennas, fourFFTs 210 corresponding to the four reception antennas, a QRdecomposition unit 220, a QRD-MLD block 230, an LLR detector 240, and aFEC 250. Also, the QRD-MLD block 230 may include a Q matrix transformer231, four inverse discrete Fourier transformers (IDFTs) 232, and fourEuclidean distance calculators (EDCs) 233.

The amount of antennas included in the device is not limited to four. Aswill be appreciated, one or more antennas, FFTs 210, IDFTs 232, and/orEDCs 233 may be used.

The FFTs 210 transform a received signal of each of the receptionantennas from a time domain signal into a signal of a frequency domain.The QR decomposition unit 220 performs QR decomposition of a channelmatrix H based on the received signals, to calculate a Q matrix and an Rmatrix.

The Q matrix transformer 231 performs an inner-product of Y and Q^(H)which are comprised of the received signals, as illustrated below inEquation 5.

$\begin{matrix}\begin{matrix}{{Q^{H}Y} = {{Q^{H}{HX}} + {Q^{H}N}}} \\{= {{Q^{H}{QRX}} + {Q^{H}N}}} \\{= {{RX} + {Q^{H}N}}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In this instance, Q^(H)Y may be expressed as given in Equation 6 below.

$\begin{matrix}{{Q^{H}Y} = {{\begin{bmatrix}R_{00} & R_{01} & R_{02} & R_{03} \\0 & R_{11} & R_{12} & R_{13} \\0 & 0 & R_{22} & R_{23} \\0 & 0 & 0 & R_{33}\end{bmatrix}\begin{bmatrix}X_{0} \\X_{1} \\X_{2} \\X_{3}\end{bmatrix}} + {Q^{H}\begin{bmatrix}n_{0} \\n_{1} \\n_{2} \\n_{3}\end{bmatrix}}}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

Referring to Equation 6, the multi-antenna signal receiving device 200is capable of sequentially detecting X₃, X₂, X₁, and X₀, because themulti-antenna signal receiving device 200 knows the R matrix and the Qmatrix.

The IDFTs 232 transform an output of the Q matrix transformer 231 from afrequency domain signal into a signal of a time domain. Referring toFIGS. 5 and 6, because the R matrix is an upper-triangular matrix, X₃through X₀ may be sequentially detected with a limited amount ofcalculations.

The EDCs 233 sequentially detect X₃ through X₀ using the R matrix. Forexample, a Euclidean distance calculator of a last stage, such as theEuclidean distance calculator of a fourth stage, detects X₃ using R₃₃,and transfers the detection result to a Euclidean distance calculator ofa third stage. In the same manner, a detection result of the Euclideandistance calculator of the third stage is transferred to an Euclideandistance calculator of the second stage, and a detection result of theEuclidean distance calculator of the second stage is transferred to aEuclidean distance calculator of a first stage. Therefore, X₃ through X₀are sequentially detected through the EDCs 233.

In this example, the EDCs 233 may detect transmission symbols using aEuclidean distance as given in Equation 7 below.

$\begin{matrix}{\arg \; \underset{Xs}{MIN}{{{Q^{H}Y} - {RXs}}}} & \left\lbrack {{Equation}\mspace{14mu} 7} \right\rbrack\end{matrix}$

As illustrated in Equation 7, Xs is a possible transmission symbol whichis a candidate transmission symbol. As an example, when a modulationscheme is 16-QAM, a number of candidate transmission symbols is sixteen.

The LLR detector 240 detects a log-likelihood ratio and the FEC 250corrects an error based on the detected log-likelihood ratio.

The multi-antenna signal receiving device 200 of FIG. 2 may obtain adiversity gain corresponding to a number of reception antennas throughQR decomposition, and may detect transmission symbols with a relativelysmall amount of calculations. However, the multi-antenna signalreceiving device 200 of FIG. 2 may struggle to equalize a distortioncaused by a multi-path interference because each of elements of achannel matrix has an independent multi-path interference.

FIG. 3 illustrates an example of a QRDE-MLD multi-antenna signalreceiving device utilizing frequency domain equalization.

Referring to FIG. 3, the QRDE-MLD multi-antenna signal receiving devicemay include four reception antennas, four FFTs 310, a QRDE-MLD block390, four IDFTs 350, four EDCs 360, an LLR detector 370, and four FECs380. In this example, the QRDE-MLD block 390 includes a Q matrixtransformer 320, subtraction/addition units 341 and 342, an additionunit 343, FDEs 331, 332, 333, and 334, and IDFTs 350.

The FFTs 310 may transform a received signal of each of the fourreception antennas from a time domain signal into a signal of afrequency domain.

The Q matrix transformer 320 may perform an inner-product on thereceived signals and the Q matrix as illustrated in Equation 6 below. Anoutput of a fourth stage of the Q matrix transformer 320 may be inputtedto two FDEs 331. The two FDEs 331 equalize the output of the fourthstage of the Q matrix transformer 320. The two FDEs 331 may provide oneof two outputs of the two FDEs 331 to the IDFTs and may provide aremaining output to subtraction/addition units 341 and 342 and anaddition unit 343 existing in a first stage, a second, and a thirdstage, respectively.

In this example, an IDFT of a fourth stage and a Euclidean distancecalculator (EDC) of the fourth stage detect X₄ using a Euclideandistance, based on an R′ matrix. The R′ matrix is a modulated R matrix,and will be further described below. The Euclidean distance calculatorof the fourth stage provides the detected X₄ to a Euclidean distancecalculator of a third stage. In this example, the Euclidean distancecalculator of the third stage detects X₃ using the detected X₄.

The subtraction/addition unit 341 receives an output of one of the twoFDEs existing in the fourth stage.

In this example, the subtraction unit included in thesubtraction/addition unit 341 removes a component corresponding to thefourth stage of the Q matrix transformer 320 from an output of the thirdstage of the Q matrix transformer 320. For example, the subtraction unitincluded in the subtraction/addition unit 341 multiplies the output ofthe FDE of the fourth stage by a predetermined subtraction coefficient,and subtracts the multiplication result from the output of the thirdstage of the Q matrix transformer 320.

The addition unit included in the subtraction/addition unit 341 adds apredetermined signal component to the output of the third stage of the Qmatrix transformer 320 to enable the output of the third stage of the Qmatrix transformer 320 and the output of the fourth stage of the Qmatrix transformer 320 to have a same variation in the frequency domain.For example, the addition unit included in the subtraction/addition 341multiplies the output of the fourth stage of the Q matrix transformer320 by a predetermined addition coefficient, and adds the multiplicationresult to the output of the third stage of the Q matrix transformer 320.

Two outputs of the subtraction/addition unit 341 are provided to twoFDEs 332. The two FDEs 332 perform equalization in the frequency domain.The two FDEs 332 generate two outputs, one of the outputs is provided toa subtraction/addition unit 342, and the remaining output is provided tothe Euclidean distance calculator of the third stage after beinginputted to an IDFT of the third stage.

The subtraction/addition unit 342 receives one of the two outputs fromthe two FDEs 331 and 332. The subtraction unit included in thesubtraction/addition unit 342 removes a component corresponding to theoutput of the fourth stage of the Q matrix transformer 320 and acomponent corresponding to the output of the third stage of the Q matrixtransformer 320 from an output of an FDE of a second stage by using apredetermined subtraction coefficient.

In this example, the addition unit included in the subtraction/additionunit 342 adds a predetermined signal component to an output of a secondstage of the Q matrix 320 to enable the output of the fourth stage ofthe Q matrix 320, the output of the third stage of the Q matrix 320, andthe output of the second stage of the Q matrix 320, to have a samevariation in the frequency domain.

Also, the two FDEs 333 equalize two outputs of the subtraction/additionunit 342 in the frequency domain. One of the two outputs of the two FDEs333 is detected through a Euclidean distance calculator of a secondstage after being inputted to an IDFT of a second stage. The remainingoutput of the two FDEs 333 is provided to the addition unit 343.

The addition unit 343 receives an output of a first stage of the Qmatrix transformer 320 and also receives one of the two outputs of thetwo FDEs 331, 332, and 333. The addition unit 343 adds a predeterminedsignal component to the output of the first stage of the Q matrixtransformer 320 to enable the output of the fourth stage of the Q matrixtransformer 320, the output of the third stage of the Q matrixtransformer 320, the output of the second stage of the Q matrixtransformer 320, and the output of the first stage of the Q matrixtransformer 320, to have a same variation in the frequency domain. Here,the subtraction is not essentially required.

An output of the addition unit 343 may be equalized through the FDE 334in the frequency domain and may be detected through the IDFT and theEuclidean distance calculator.

The LLR detector 370 may detect a log-likelihood ratio and provide thedetected log-likelihood ratio to a plurality of FECs 380. In thisexample, the plurality of FECs 380 perform error correction. A multipleuser MIMO communication system may use a plurality of FECs 380 A singleuser MIMO communication system may use a single FEC.

FIG. 4 illustrates an operation of an exemplary subtraction/additionunits 341 and 342, exemplary addition unit 343, and exemplary FDEs 331,332, 333, and 334 that may be incorporated into the QRDE-MLDmulti-antenna receiving device of FIG. 3.

Referring to FIG. 4, a Q matrix transformer 410 outputs Q^(H)Y[3],Q^(H)Y[2], Q^(H)Y[1], and Q^(H)Y[0] for each stage. In this example,Y[x] is an x^(th) element of a Y vector.

The two FDEs 331 perform equalization of the Q^(H)Y[3] usingequalization coefficients FDE_AddW[3] and FDE_SubW[3]. In this example,an upper FDE of the two FDEs 331 corresponds to a multiplication unit422, and a lower FDE corresponds to a multiplication unit 421.

The multiplication unit 421 performs an inner-product of the FDE_AddW[3]with the Q^(H)Y[3], and the multiplication unit 422 performs aninner-product of the FDE_SubW[3] with the Q^(H)Y[3]. The FDE_AddW[3] andthe FDE_SubW[3] may be expressed as illustrated below in Equation 8.

$\begin{matrix}\frac{R_{33}^{H}}{{R_{33}^{H}R_{33}} + \frac{N}{S}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

An output of the multiplication unit 422 is provided to asubtraction/addition unit 430 of a third stage.

A multiplication unit 431 performs an inner-product of the output of themultiplication unit 422 with an addition coefficient AddW[2][3]. Also,an addition unit 432 adds an output of the multiplication unit 431 andthe Q^(H)Y[2]. In this example, the output of the multiplication unit431 is added to the Q^(H)Y[2] to enable the Q^(H)Y[3] and the Q^(H)Y[2]to have a same variation in the frequency domain.

For example, the AddW[2][3] may be expressed as illustrated below inEquation 9.

$\begin{matrix}{{{AddW}_{{\lbrack 2\rbrack}{\lbrack 3\rbrack}}(\omega)} = {\left( {{\frac{\overset{\_}{R_{23}}}{\overset{\_}{R_{22}}}R_{22}} - R_{23}} \right).}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

In this example, R_(xy) is a mean vector of a y sub-stream in a stage x.

The output of the multiplication unit 422 is provided to amultiplication unit 433. The multiplication unit 433 performs aninner-product of a subtraction coefficient SubW[2][3] and the output ofthe multiplication unit 422. Also, an output of the multiplication unit433 is provided to a subtraction unit 434. A subtraction unit 434subtracts the output of the multiplication unit 433 from the Q^(H)Y[2].Accordingly, a component corresponding to the Q^(H)Y[3] may be removedfrom the Q^(H)Y[2]. The SubW[2][3] may be expressed as illustrated belowin Equation 10.

SubW _([2][3])(ω)=R ₂₃  [Equation 10]

An output of the addition unit 432 may be expressed as illustrated belowin Equation 11.

$\begin{matrix}{{{\left\{ {Q^{H}Y} \right\} \lbrack 2\rbrack} + {{{{AddW}\lbrack 2\rbrack}\lbrack 3\rbrack}{{FDE\_ Sub}\lbrack 3\rbrack}{\left\{ {Q^{H}Y} \right\} \lbrack 3\rbrack}}} = {{{R_{22}X_{2}} + {R_{23}X_{3}} + n_{2} + {\left( {{\frac{\overset{\_}{R_{23}}}{\overset{\_}{R_{22}}}R_{22}} - R_{23}} \right)\frac{R_{33}^{H}}{{R_{33}^{H}R_{33}} + \frac{N}{S}}\left( {{R_{33}X_{3}} + n_{3}} \right)}} = {{{{R_{22}X_{2}} + {R_{23}X_{3}} + n_{2} + {\left( {{\frac{\overset{\_}{R_{23}}}{\overset{\_}{R_{22}}}R_{22}} - R_{23}} \right)X_{3}}}\because{highSNR}} = {{{R_{22}X_{2}} + {\frac{\overset{\_}{R_{23}}}{\overset{\_}{R_{22}}}R_{22}X_{3}} + n_{2}} = {{R_{22}\left\{ {X_{2} + {\frac{\overset{\_}{R_{23}}}{\overset{\_}{R_{22}}}X_{3}}} \right\}} + n_{2}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

In Equation 11, for ease of description, n₃ or a noise of anequalization coefficient is regarded as ‘0’.

The multiplication unit 422 corresponding to an FDE of the third stageperforms an inner-product of an equalization coefficient FDE_SubW[2]with an output of a subtraction unit 434. The equalization coefficientFDE_SubW[2] may be expressed as illustrated below in Equation 12.

$\begin{matrix}{{{{FDE\_ SubW}\lbrack 2\rbrack} = \frac{R_{22}^{H}}{{R_{22}^{H}R_{22}} + \frac{N}{S}}},} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack\end{matrix}$

A multiplication unit 441 performs an inner-product of the output of theaddition unit 432 with the FDE_AddW[2]. The FDE_AddW[2] may be expressedas illustrated below in Equation 13.

$\begin{matrix}{{{{FDE\_ AddW}\lbrack 2\rbrack} = \frac{R_{22}^{H}R_{2{Sum}}}{{R_{ss}^{H}R_{22}R_{2{Sum}}} + \frac{N}{S}}},{R_{2{Sum}} = \frac{\sum\limits_{m = 2}^{3}{\overset{\_}{R_{2m}}}^{2}}{{\overset{\_}{R_{22}}}^{2}}}} & \left\lbrack {{Equaiton}\mspace{14mu} 13} \right\rbrack\end{matrix}$

In this example, a size of N/S may be set as an appropriate valueaccording to a communication environment.

A subtraction coefficient SubW[x][y], an addition coefficientAddW[x][y], an equalization coefficient FDE_SubW[x], and an equalizationcoefficient FDE_AddW[x], may be generalized as illustrated below inEquation 14. One or more of the subtraction coefficient, the additioncoefficient, and the equalization coefficients may be used in eachstage.

$\begin{matrix}{{{SubW}_{{\lbrack x\rbrack}{\lbrack y\rbrack}} = R_{xy}}{{AddW}_{{\lbrack x\rbrack}{\lbrack y\rbrack}} = \left( {{\frac{\overset{\_}{R_{xy}}}{\overset{\_}{R_{xx}}}R_{xx}} - R_{xy}} \right)}{{FDE\_ SubW}_{\lbrack x\rbrack} = \frac{R_{xx}^{H}}{{R_{xx}^{H}R_{xx}} + \frac{N}{S}}}{{{FDE\_ AddW}_{\lbrack x\rbrack} = \frac{R_{xx}^{H}R_{xSum}}{{R_{xx}^{H}R_{xx}R_{xSum}} + \frac{N}{S}}},{R_{xSum} = \frac{\sum\limits_{m = x}^{N_{RX} - 1}{\overset{\_}{R_{xm}}}^{2}}{{\overset{\_}{R_{xx}}}^{2}}}}} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

The R matrix may be required to be modulated as an R′ matrix due to anexistence of the subtraction unit or the addition unit.

The R′ may be expressed as illustrated below in Equation 15.

$\begin{matrix}\begin{matrix}{R_{xt}^{\prime} = {\left( {R_{xy} + {R_{yy}W_{suby}{AddW}_{xy}}} \right)W_{addx}}} \\{= {\begin{Bmatrix}{R_{xy} +} \\{\left( {{\frac{\overset{\_}{R_{xy}}}{\overset{\_}{R_{xx}}}R_{xx}} - R_{xy}} \right)\frac{{R_{yy}}^{2}}{{R_{yy}}^{2} + \frac{N}{S}}}\end{Bmatrix}\frac{R_{xx}^{H}R_{xSum}}{{{R_{xx}}^{2}R_{xSum}} + \frac{N}{S}}}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 15} \right\rbrack \\{\mspace{79mu} {R_{xSum} = \frac{\sum\limits_{m = x}^{N_{RX} - 1}{\overset{\_}{R_{xm}}}^{2}}{{\overset{\_}{R_{xx}}}^{2}}}} & \;\end{matrix}$

An exemplary procedure of processing streams of a third stage and afourth stage has been described, and thus, a procedure of processingstreams of a first stage and a second stage will be omitted.

The QRDE-MLD multi-antenna signal receiving device may perform, for eachstage, equalization of a signal variation in the frequency domain bycorrecting a signal of a lower stage in a predetermined stage through anaddition unit, to correct distortion caused by an MPI. The QRDE-MLDmulti-antenna signal receiving device may detect a transmission symbolby eliminating a component corresponding to a signal of the lower stagefrom a signal of the predetermined stage.

However, the QRDE-MLD multi-antenna receiving device in a broadbandapplication may not sufficiently compensate for the distortion caused bythe MPI because QR decomposition generally increases a frequencyselectivity.

FIG. 5 illustrates a second example of a QRDE-MLD multi-antenna signalreceiving device.

Referring to FIG. 5, the QRDE-MLD multi-antenna signal receiving devicemay include, among other things, four reception antennas, four FFTs 510,and a Q matrix transformer 520.

A basic operation of the QRDE-MLD multi-antenna signal receiving deviceof FIG. 5 is the same as an operation of the QRDE-MLD multi-antennasignal receiving device of FIGS. 3 and 4. However, the QRDE-MLDmulti-antenna signal receiving device of FIG. 5 re-inputs a signal toaddition units 521 and 524 and subtraction/addition units 522 and 523,through a re-modification unit 591 and a DFT 592. The re-inputted signalundergoes a process of detection and error correction.

In this example, an addition coefficient used by the addition units 521and 524 and the subtraction/addition unit 522 and 523 may be expressedas illustrated below in Equation 16.

$\begin{matrix}{{{AddW}_{{\lbrack x\rbrack}{\lbrack y\rbrack}} = \left( {{\frac{\overset{\_}{R_{xy}}}{\overset{\_}{R_{xx}}}R_{xx}} - R_{xy}} \right)},{y \neq x}} & \left\lbrack {{Equation}\mspace{14mu} 16} \right\rbrack\end{matrix}$

FIG. 6 illustrates an exemplary addition unit and an exemplary frequencydomain equalizer that may be incorporated into the QRDE-MLDmulti-antenna signal receiving device of FIG. 5.

Referring to FIG. 6, the addition units 521 and 524 include a pluralityof multiplication units 621, 622, 623, and 624. The addition units 521and 524 also include a plurality of addition units 611, 612, 613, and614.

The plurality of multiplication units 621, 622, 623, and 624 perform aninner-product of output signals of the DFT 592 with additioncoefficients as illustrated above in Equation 16. The outputs of themultiplication units 621, 622, 623, and 624 are provided to the additionunits 611, 612, 613, and 614.

The addition unit 611 performs an inner-product of an output of themultiplication unit 621 with Q^(H)Y[X]. Also, an output of the additionunit 611 is provided to a neighboring addition unit 612. The additionunit 612 adds the output of the addition unit 611 and an output of themultiplication unit 622. The addition unit 613 adds an output of theaddition unit 612 and an output of the multiplication unit 623. Theaddition unit 614 also adds an output of the addition unit 613 and anoutput of the multiplication unit 624.

The multiplication unit 630 performs equalization of the output of theaddition unit 614 using an equalization coefficient FDE_AddW[X] in thefrequency domain.

FIG. 7 illustrates an exemplary subtraction/addition unit and thefrequency domain equalizer that may be incorporated into the QRDE-MLDmulti-antenna signal receiving device of FIG. 5.

Referring to FIG. 7, the subtraction/addition unit includes a pluralityof addition units 731, 732, and 733, a plurality of subtraction units721, 722, and 723, and a plurality of multiplication units 711, 712,713, 714, 741, 742, 743, 751, and 752.

The multiplication unit 711 performs an inner-product of an output ofDFT 592 as illustrated in FIG. 5, with an addition coefficientAddW[X][3] and provides the result to the addition unit 731. Themultiplication unit 712 performs an inner-product of the output of theDFT 592 with an addition coefficient AddW[X][2] and provides the resultto the addition unit 732. The multiplication unit 713 performs aninner-product of the output of the DFT 592 with an addition coefficientAddW[X][1] and provides the result to the addition unit 733.

The multiplication unit 741 performs an inner-product of the output ofthe DFT 592 with an addition coefficient SubW[X][3] and provides theresult to the subtraction unit 721. The multiplication unit 742 performsan inner-product of the output of the DFT 592 with an SubW[X][2] andprovides the result to the subtraction unit 722. The multiplication unit743 performs an inner-product of the output of the DFT 592 with anaddition coefficient SubW[X][1] and provides the result to thesubtraction unit 723.

The addition unit 731 adds Q^(H)Y[X] and an output of the multiplicationunit 711, the addition unit 732 adds an output of the addition unit 731and an output of the multiplication unit 712, and the addition unit 733adds an output of the multiplication unit 713 and an output of theaddition unit 732.

The subtraction unit 721 subtracts an output of the multiplication unit741 from the Q^(H)Y[X], the subtraction unit 722 subtracts an output ofthe multiplication unit 742 from an output of the subtraction unit 721,and the subtraction unit 723 subtracts an output of the subtraction unit743 from an output of the subtraction unit 722.

The subtraction unit 751 performs equalization of an output of theaddition unit 733 by using an equalization coefficient FDE_AddW[X] in afrequency domain. Also, the multiplication unit 752 performsequalization of an output of the subtraction unit 723 by using anequalization coefficient FDE_SubW[X].

FIG. 8 is a diagram illustrating a multi-path interference.

Referring to FIG. 8, a transmission symbol may be transmitted from asingle transmission antenna to one or more reception antennas via aplurality of paths. For example, a received signal a₁ of a receptionantenna 1 includes a component a₁₁ arriving via a path 1-1 and acomponent a₁₂ arriving via a path 1-2. A received signal a₂ of areception antenna 2 includes a component a₂₁ arriving via a path 2-1 anda component a₂₂ arriving via a path 2-2. Exemplary graphs in which a₁₁and a₁₂ constituting a₁, and a₂₁ and a₂₂ constituting a₂, areillustrated on the right-hand side of FIG. 8

FIG. 9 is a block diagram illustrating an example of an MPIC-QRDE-MLDmulti-antenna signal receiving device.

Referring to FIG. 9, the exemplary MPIC-QRDE-MLD multi-antenna signalreceiving device may include two reception antennas, FFTs 910, a firstdetector 920, a second detector 930, and a combining unit 940. Althoughthe MPIC-QRDE-MLD multi-antenna signal receiving device is capable ofincluding more than or less than two reception antennas, for ease ofdescription, a case of having two reception antennas will be describedwith reference to FIG. 9. Also, for ease of convenience, in this examplea single transmission antenna transmits a symbol “a” included in asingle stream.

As described in the description with reference to FIG. 8, it is assumedthat a received signal of a reception antenna 1 is a₁ and a receivedsignal of a reception antenna 2 is a₂. As illustrated in graphs 950 and970, the received signal a₁ of the reception antenna 1 includes acomponent a₁₁ arriving via a path 1-1 and a component a₁₂ arriving via apath 1-2. The received signal a₂ of the reception antenna 2 includes acomponent a₂₁ arriving via a path 2-1 and a component a₂₂ arriving via apath 2-2.

The first detector 920 includes a first multi-path interferenceeliminating unit 921 and a first QRDE block 922. The second detector 930includes a second multi-path interference eliminating unit 931 and asecond QRDE block 932. In this example, the first QRDE block 922 and thesecond QRDE block 932 may perform the same operation as the QRDE blocks390 and 590 described with reference to FIGS. 3 through 7, and thusdetailed description thereof will be omitted.

The first detector 920 and the second detector 930 process receivedsignals of reception antennas for each path. The first detector 920processes the component a₁₁ corresponding to a path having a highestgain among components a₁₁ and a₁₂ of a₁ and also processes the componenta₂₁ corresponding to a path having a highest gain among components a₂₁and a₂₂ of a₂. The second detector 930 processes the component a₁₂corresponding to a path having a lowest gain among components a₁₁ anda₁₂ of a₁ and also processes the component a₂₂ corresponding to a pathhaving a lowest gain among components a₂₁ and a₂₂ of a₂.

For example, the first multi-path interference eliminating unit 921removes a multi-path interference existing in the received signal a₁ ofthe reception antenna 1 and the received signal a₂ of the receptionantenna 2, based on a stream or a transmission symbol detected from aprior iteration.

An output of the DFT 592 of FIG. 5, which is a stream detected from aprior iteration, is provided to the first multi-path interferenceeliminating unit 921 and the second multi-path interference eliminatingunit 922. The first multi-path interference eliminating unit 921 and thesecond multi-path interference eliminating unit 922 removes a multi-pathinterference from the received signal a₁ of the reception antenna 1 andthe received signal a₂ of the reception antenna 2, based on the outputof the DFT 592, such as the stream detected from the prior iteration.

In this example, the first multi-path interference eliminating unit 921outputs a component corresponding to a path having a highest gain fromeach of the received signal a₁ and the received signal a₂, and removesthe remaining components. For example, the received signal a₁ of thereception antenna 1 includes the components a₁₁ and a₁₂, and thecomponent a₁₁ corresponds to the path having the highest gain among a₁₁and a₁₂. The first multi-path interference eliminating unit 921 removesthe component a₁₂ from the received signal a₁ of the reception antenna 1and outputs the component a₁₁. The first multi-path interferenceeliminating unit 921 removes the component a₂₂ from the components a₂₁and a₂₂ included in the received signal a₂ of the reception antenna 2.

In this example, the second multi-path interference eliminating unit 922outputs components corresponding to a path having a second highest gain.The second multi-path interference eliminating unit 922 removes thecomponent a₁₁ from the received signal a₁ of the reception antenna 1 andoutputs the component a₁₂. The second multi-path interferenceeliminating unit 922 removes the component a₂₁ from the components a₂₁and a₂₂ included in the received signal a₂ of the reception antenna 2,and outputs the component a₂₂.

Outputs of the first multi-path interference eliminating unit 921 andthe second multi-path interference eliminating unit 922 may beillustrated as shown in graphs 960 and 980. Referring to graph 960, anoutput of a lower end among outputs of the first multi-path interferenceeliminating unit 921 is the component a₂₁ corresponding to a path havinga highest gain among the components a₂₁ and a₂₂. An output of an upperend among outputs of the second multi-path interference eliminating unit922 is the component a₁₂ corresponding to a path having a lowest gainamong the components a₁₁ and a₁₂. Although not illustrated in FIG. 9,the output of the upper end among the outputs of the first multi-pathinterference eliminating unit 921 may be a₁₁ that is corresponding tothe path having highest gain among components a₁₁ and a₁₂ of a₁, and theoutput of the lower end among the outputs of the second multi-pathinterference eliminating unit 922 may be a₂₂ that is corresponding tothe path having the lowest gain among components a₂₁ and a₂₂ of a₂.

A first QRDE block 922 performs detection with respect to the a₁₁ anda₁₂. In this example, the first QRDE block 922 performs functions of theQRDE blocks 390 and 590 as described with reference to FIGS. 3 through7, and enables estimation of “a” based on a₁₁ and a₂₁. In the samemanner, a second QRDE block 932 estimates “a” based on a₁₂ and a₂₂.Also, “a” estimated by the first QRDE block 922 and the second QRDEblock 932 is provided to a combining unit 940, and the combining unit940 combines “a” estimated by the first QRDE block 922 and the secondQRDE block 932 to accurately estimate “a”. In this example, an output ofthe combining unit 940 may be processed through an IDFT, an EDE, a LLR,a FEC, and the like (not illustrated).

Although not illustrated in FIG. 9, the QRDE block 922 of the firstdetector 920 may include a first Q matrix transformer that transformsa₁₁ and a₂₁ using a Q matrix, a plurality of first FDEs performingequalization of outputs of the first Q matrix transformers in afrequency domain prior to performing Inverse Fourier Transform, and aplurality of first IDFTs performing Inverse Discrete Fourier Transformwith respect to outputs of the plurality of first FDEs. In the samemanner, the QRDE block 922 of the second detector 930 may include asecond Q matrix transformer that transforms a₁₂ and a₂₂ by using a Qmatrix, a plurality of second FDEs performing equalization of outputs ofthe second Q matrix transformers in the frequency domain prior toperforming Inverse Fourier Transform, and a plurality of second IDFTsperforming Inverse Discrete Fourier Transform with respect to outputs ofthe plurality of second FDEs.

The MPIC-QRDE-MLD multi-signal receiving device removes the multi-pathinterference with a limited amount of calculations, and also processes areceived signal of each reception antenna for each path, therebyobtaining a full diversity gain.

FIG. 10 is a diagram illustrating a received signal of each of fourreception antennas, when four transmission antennas and the fourreception antennas exist.

Referring to FIG. 10, it is assumed that the transmission antennas 1, 2,3, and 4 respectively transmit a, b, c, and d streams or transmissionsymbols. Also, a received signal r₁ of the reception antenna 1 includesa component a₁ related to the a stream, a component b₁ related to the bstream, a component c₁ related to the c stream, and a component d₁related to the d stream. In the same manner, a received signal r₂ of thereception antenna 2 includes a component a₂ related to the a stream, acomponent b₂ related to the b stream, a component c₂ related to the cstream, and a component d₂ related to the d stream. Also, a receivedsignal r₃ of the reception antenna 3 includes a component a₃ related tothe a stream, a component b₃ related to the b stream, a component c₃related to the c stream, and a component d₃ related to the d stream.Also, a received signal r₄ of the reception antenna 4 includes acomponent a₄ related to the a stream, a component b₄ related to the bstream, a component c₄ related to the c stream, and a component d₄related to the d stream.

In this example, a₁, a₂, a₃, a₄, b₁, b₂, b₃, b₄, c₁, c₂, c₃, c₄, d₁, d₂,d₃, and d₄ also include components corresponding to a plurality of pathsdue to the multiple paths. For the ease of description, it is assumedthat components included in a₁ are represented as a₁₁, a₁₂, . . . ,a_(1N) and components included in b₁ are represented as b₁₁, b₁₂, . . ., b_(1N), in an order of a highest gain of a corresponding path.Although not illustrated in FIG. 10, the components included in a₂ arealso represented as a₂₁, a₂₂, . . . , a_(2n) in an order of a highestgain of a corresponding path, and the components of a3, a₄, b₁, b₂, b₃,b₄, c₁, c₂, c₃, c₄, d₁, d₂, d₃, and d₄ are also represented in the samemanner.

FIG. 11 illustrates detectors and combining units of an MPIC-QRDE-MLDmulti-antenna signal receiving device for processing the received signalof each of the four reception antennas of FIG. 10.

Referring to FIG. 11, the MPIC-QRDE-MLD multi-antenna signal receivingdevice may include a plurality of detectors. In some embodiments thedetectors comprise the same structure.

A first detector may process a component corresponding to a path havinga highest gain among components included in a₁, a₂, a₃, a₄, b₁, b₂, b₃,b₄, c₁, c₂, c₃, c₄, d₁, d₂, d₃, and d₄. Hereinafter, the multi-pathinterference eliminating unit is referred to as interference eliminatingunit. As an example, a first interference eliminating unit may extractand output (a₁₁, b₁₁, c₁₁, d₁₁), (a₂₁, b₂₁, c₂₁, d₂₁), (a₃₁, b₃₁, c₃₁,d₃₁), (a₄₁, b₄₁, c₄₁, d₄₁) from r₁, r₂, r₃, and r₄. A second detectormay process a component corresponding to a path having a second highestgain among the components included in a₁, a₂, a₃, a₄, b₁, b₂, b₃, b₄,c₁, c₂, c₃, c₄, d₁, d₂, d₃, and d₄. Accordingly, a second interferenceeliminating unit of the second detector may extract and output (a₁₂,b₁₂, c₁₂, d₁₂), (a₂₂, b₂₂, c₂₂, d₂₂), (a₃₂, b₃₂, c₃₂, d₃₂), (a₄₂, b₄₂,c₄₂, d₄₂) from r₁, r₂, r₃, and r₄. In the same manner, a secondinterference eliminating unit of an n^(th) detector may extract andoutput (a_(1N), b_(1N), c_(1N), d_(1N)), (a_(2N), b_(2N), c_(2N),d_(2N)), (a_(3N), b_(3N), c_(3N), c_(3N)), (a_(4N), b_(4N), c_(4N),d_(aN)) from r₁, r₂, r₃, and r₄.

QRDE blocks estimate streams “a”, “b”, “c”, and “d” based on outputs ofthe interference eliminating units. In this example, the QRDE blocksperform QR decomposition detection and frequency domain equalizationbased on the outputs of interference eliminating units as described withreference FIGS. 3 through 7.

The outputs of the QRDE blocks are provided to the combining units. Afirst output of a first QRDE block, a first output of a second QRDEblock, and a first output of an N^(th) QRDE block, which are related to“a”, are provided to a combining unit of an uppermost stage, and thecombining unit of the uppermost stage combines the first outputs of theQRDE blocks to gain a full diversity gain and to estimate “a”. An outputof the combining unit of the uppermost stage may be processed throughIDFT, EDE, LLR, FEC, and the like which are not illustrated in FIG. 11.In the same manner, a combining unit of a second stage combines secondoutputs of the QRDE blocks to estimate “b”, a combining unit of a thirdstage combines third outputs of the QRDE blocks to estimate “c”, and acombining unit of a fourth stage combines fourth outputs of the QRDEblocks to estimate “d”.

The methods described above may be recorded, stored, or fixed in one ormore computer-readable storage media that includes program instructionsto be implemented by a computer to cause a processor to execute orperform the program instructions. The media may also include, alone orin combination with the program instructions, data files, datastructures, and the like. Examples of computer-readable media includemagnetic media, such as hard disks, floppy disks, and magnetic tape;optical media such as CD ROM disks and DVDs; magneto-optical media suchas optical disks; and hardware devices that are specially configured tostore and perform program instructions, such as read-only memory (ROM),random access memory (RAM), flash memory, and the like. Examples ofprogram instructions include machine code, such as produced by acompiler, and files containing higher level code that may be executed bythe computer using an interpreter. The described hardware devices may beconfigured to act as one or more software modules in order to performthe operations and the methods described above, or vice versa.

A number of exemplary embodiments have been described above.Nevertheless, it will be understood that various modifications may bemade. For example, suitable results may be achieved if the describedtechniques are performed in a different order and/or if components in adescribed system, architecture, device, or circuit are combined in adifferent manner and/or replaced or supplemented by other components ortheir equivalents. Accordingly, other implementations are within thescope of the following claims.

1. A multi-antenna signal receiving device, comprising: at least twoantennas to receive at least one stream, a received signal of a firstantenna including components corresponding to a plurality of first pathsand a received signal of a second antenna including componentscorresponding to a plurality of second paths; a first detector to detecta component corresponding to a first path of the plurality of firstpaths from among components included in the received signal of the firstantenna, and to detect a component corresponding to a second path of theplurality of second paths from among components included in the receivedsignal of the second antenna; a second detector to detect a componentcorresponding to the remaining first paths of the plurality of firstpaths from among the components included in the received signal of thefirst antenna, and to detect a component corresponding to the remainingsecond paths of the plurality of second paths from among the componentsincluded in the received signal of the second antenna; and a combiningunit to combine the detected component from the first detector and thedetected component from the second detector, to detect the at least onestream.
 2. The device of claim 1, further comprising: a QR decompositionunit to perform QR decomposition with respect to a channel matrix basedon the received at least one stream, to calculate a Q matrix and an Rmatrix.
 3. The device of claim 2, wherein the first detector removes amulti-path interference existing in the received signal using at leastone stream detected from a prior iteration, extracts the componentcorresponding to the first path from among the components included inthe received signal of the first antenna, and detects the at least onestream using the Q matrix and the R matrix.
 4. The device of claim 2,wherein the first detector comprises a first multi-path interferenceeliminating unit to remove a multi-path interference existing in thereceived signal of the first antenna using at least one stream detectedfrom a prior iteration, and to extract the component corresponding tothe first path from among the components included in the received signalof the first antenna.
 5. The device of claim 3, wherein the first pathhas a higher gain than the remaining first paths of the plurality offirst paths.
 6. The device of claim 4, wherein the first detectorfurther comprises a first Q matrix transformer to transform thecomponent corresponding to the first path of the plurality of firstpaths using the Q matrix.
 7. The device of claim 6, wherein the firstdetector further comprises a plurality of first frequency domainequalizers (FDEs) to perform equalization of an output of the first Qmatrix transformer in a frequency domain prior to performing InverseFourier Transform.
 8. The device of claim 7, wherein the first detectorfurther comprises a plurality of first Inverse Discrete FourierTransformers (IDFTs) to perform Inverse Discrete Fourier Transform withrespect to outputs of the plurality of the first FDEs.
 9. The device ofclaim 3, wherein the first detector further removes a multi-pathinterference existing in the received signal of the second antenna usingat least one stream detected from a prior iteration, extracts thecomponent corresponding to the second path from among the componentsincluded in the received signal of the second antenna, and detects theat least one stream using the Q matrix and the R matrix.
 10. The deviceof claim 4, wherein the first multi-path interference eliminating unitfurther removes a multi-path interference existing in the receivedsignal of the second antenna using at least one stream detected from aprior iteration, and extracts the component corresponding to the secondpath from among the components included in the received signal of thesecond antenna.
 11. The device of claim 2, wherein the second detectorcomprises a second multi-path interference eliminating unit to remove amulti-path interference existing in the received signal of the firstantenna using at least one stream detected from a prior iteration, andto extract the component corresponding to the remaining first paths fromamong the components included in the received signal of the firstantenna.
 12. The device of claim 11, wherein the second multi-pathinterference eliminating unit further removes a multi-path interferenceexisting in the received signal of the second antenna using at least onestream detected from a prior iteration, and extracts the componentcorresponding to the remaining second paths from among the componentsincluded in the received signal of the second antenna.
 13. The device ofclaim 11, wherein the second detector further comprises a second Qmatrix transformer to transform the component corresponding to theremaining first paths and the component corresponding to the remainingsecond paths using the Q matrix.
 14. The device of claim 13, wherein thesecond detector further comprises a plurality of second FDEs to performequalization of an output of the second Q matrix transformer in afrequency domain prior to performing Discrete Inverse Fourier Transform.15. The device of claim 14, wherein the second detector furthercomprises a plurality of second IDFTs to perform Inverse DiscreteFourier Transform with respect to outputs of the plurality of secondFDEs.